Unknown Format Error on Submitting a PDF from the Adobe Acrobat

I am working on a project that requires submitting the content of the PDF document as a stream to a Servlet. For the most part, the project works fine – the form is posted by the Acrobat/Reader, the server receives the file, creates a local copy and processes it correctly. After the post is successfully received, the last step on the server is to send a reply to the Acrobat/Reader. On not receiving a reply, the Adobe Acrobat/Reader throws an unknown format error.

Reason of the problem is that the Adobe Acrobat/ Reader expect a return from the servlet and the application server was not generating a response that Acrobat/Reader understands. To remove the error message, the servlet should return a properly constructed FDF and the URL of the submit button should end with #FDF.

Note:I am using Adobe LiveCycle Designer; I believe you can use Adobe Acrobat to achieve the same result.

Here are the exact steps to remove the error:

Open your XDP form in LiveCycle Designer.

Select the Submit button.

Either in the Design View or in the Source view, edit submit to URL to add #FDF at the end of the URL.

Save the XDP.

In your Java project, create a plain-text file and add the following content: